1. Field of the Invention
The present invention relates to an equipment for manufacturing a semiconductor device using a solid source such as a silicon molecular beam epitaxy equipment (hereinafter referred to as "Si-MBE") or a vapor deposition equipment.
2. Description of the Related Art
A conventional solid source Si-MBE is structured as shown in FIG. 1. In the figure, reference numeral 1 denotes a Si solid source; 2, a copper hearth; 7, a growth chamber; 8, a wafer exchange chamber; 9, a wafer rotary heating mechanism; 10, a liquid nitrogen shroud for cooling the device; 11, a wafer; 12, a port with an impurity vapor deposition source cell; and 13, a crucible for the impurity vapor deposition source cell. Si crystal growth was conducted by putting the wafer 11 on the wafer rotary heating mechanism 9 in such a manner that a surface of the wafer 11 from which crystal grows is directed downward, and melting the Si solid source 1 by electron beams irradiated from an E-GUN filament (not shown) within the solid source copper hearth 2 which is located centrally at the lower side of the growing chamber 7 to evaporate the melted solid source 1 as molecular beams. Also, impurity doping is conducted by evaporating impurities inserted into the crucible 13 for the impurity vapor deposition source cell simultaneously during the Si growth.
The conventional Si solid source 1 is inserted into the exclusive copper hearth 2 having a hole defined in the upper portion thereof where the solid source is located, and the amount of decrease of the Si solid source has been recognized from a view port provided in the growing chamber by operator's eyes. The procedure will be described with reference to the structural cross-sectional view of the hearth as follows.
FIG. 2A shows a structural cross-sectional view showing the solid source copper hearth for use in the conventional solid source Si-MBE or vapor deposition equipment. In the figure, reference numeral 3 denotes an E-GUN filament, and 4 is a deflecting lens. The electron beams outputted from the E-GUN filament 3 are irradiated onto the upper surface of the solid source 1 through the deflecting lens 4 so as to melt and evaporate a part of the Si source. Hence, as the source is consumed, the source surface becomes hollow as shown in FIG. 2B. A change in the hollow shape of the source surface is recognized mainly by eye to determine timing of exchanging the source.
However, in the conventional technique, it was difficult to recognize an actual condition depthwise of the source surface because its normal work cannot be performed under the atmosphere in an ultra high vacuum equipment. Also, there is a case in which there is the vapor deposition source at a position which is difficult to recognize from the view port defined in the growth chamber. In this case, unless the use limit is grasped, the Si source 1 disappears at the electron beams irradiating portion as shown in FIG. 3. As a result, the electron beams from the E-GUN filament 3 are directly irradiated onto the bottom portion of the copper hearth 2, whereby Cu atoms of the hearth material instead of Si spread over the growing chamber as molecular beams, resulting in the possibility that the device is contaminated by heavy metal. The contamination due to the heavy metal induces an epitaxial crystal defect and dislocation, and the crystal defect and dislocation allow such a characteristic deterioration as an increase in leak current during manufacturing the device. Moreover, with the continuation of this state, there is a case in which not only the device is contaminated by Cu but also the bottom portion of the hearth is damaged.
In view of the above, up to now, timing of exchanging the vacuum deposition source was set by controlling the total amount of use of the solid source using a film thickness integrating meter, or timing of exchanging the vacuum deposition source was recognized by eye. However, these methods were improper as a mass production equipment because they largely depended on experience of a worker.
Also, to solve the above problem, there has been attempted a proposal in which an X-ray source and an X-ray receiving portion are fixed, respectively, onto both sides of a fixing port of a cell into which a vapor deposition source is inserted, to manage a remaining amount of the vapor deposition source as an X-ray transmission image (Japanese Patent Unexamined Publication No. Hei 2-51489).
However, that proposal requires that the vapor deposition source is inserted into the cell, and also that there arise, because an X-ray source 15 and an X-ray receiving portion 16 are required for each cell, a problem relating to a safety management from the viewpoint of the property of X-rays, and a problem relating to an increase of the management costs caused by the safety management, and so on. Therefore, the proposal is improper for a mass production equipment to be dealt with by a large number of unspecified workers. Furthermore, the hearth for the Si solid source normally used in the Si-MBE is located in the center of a growth chamber which is kept in an ultra high vacuum state, and the outer configuration of the Si solid source is not changed even though the X-ray transmission image is observed from the exterior of the equipment. As a result, it was difficult to regognize the accurate remaining amount.